Keys Not Registering on 122-Key Model M

[HanSoloCup]

Hey everyone! I just made an account here because I need help with a terminal Model M I bought recently. Its missing 3 key caps and was in some pretty rough shape when I got it, but it seemed like a good deal for $30. After doing some cleaning it was looking good, and it didn't really seem like it needed to be bolt-modded to me. After making an adapter for my Teensy 2.0 to use Soarer's Converter (which I have checked over and over and have confirmed to be 100% wired correctly), using HID Listen showed that a bunch of keys weren't working.When I pressed them, nothing happened at all, not even an incorrect register. Below I have pictures of my setup and anything I thought could be useful. Thanks!


The keys that aren't working highlighted in yellow.


The model info on the back of the case.


My setup for Soarer's Converter (I have a case for the Teensy on the way, and I am absolutely positive everything here is wired correctly).


The PCB.


The longer connector's contacts.


The shorter connector's contacts.


The shorter connector seems to be attached to the larger one, but it looks like it's coming off.

Thanks again for any help and advice!

[fslice]

Hey, I'm new here too. But I just so happen to be working on a couple M122s right now, so I figured I can try to lend you a hand.

First, try to reseat your ribbon cables. If keys still fail, you might need to do a bolt mod and fix 6 traces.

There's a small chance your broken traces are at the end ribbon and you might be able to fix them without having to do a bolt mod. But most likely you will need to disassemble - your membrane stack should look like this when you do:



Based on your keys, it looks like only your bottom sheet is damaged, in 6 traces. I highlighted your keys and traces you need to check - use a multimeter and test resistance (undamaged should be 30 Ohms or so, but they should work with up to 100 or even more):



Failed keys are circled in red, broken traces are along the green crosses. Edit: I missed a green X in the middle alpha cluster.

To fix broken traces, I've used conductive ink with success. Do some shopping online and check old threads here to see some examples. This should get you started, good luck and let us know how it goes!

[HanSoloCup]

Hey, I'm new here too. But I just so happen to be working on a couple M122s right now, so I figured I can try to lend you a hand.

First, try to reseat your ribbon cables. If keys still fail, you might need to do a bolt mod and fix 6 traces.

There's a small chance your broken traces are at the end ribbon and you might be able to fix them without having to do a bolt mod. But most likely you will need to disassemble - your membrane stack should look like this when you do:



Based on your keys, it looks like only your bottom sheet is damaged, in 6 traces. I highlighted your keys and traces you need to check - use a multimeter and test resistance (undamaged should be 30 Ohms or so, but they should work with up to 100 or even more):



Failed keys are circled in red, broken traces are along the green crosses. Edit: I missed a green X in the middle alpha cluster.

To fix broken traces, I've used conductive ink with success. Do some shopping online and check old threads here to see some examples. This should get you started, good luck and let us know how it goes!

Thanks for the reply! Yeah, I figured I'd have to open it up and then bolt-mod it. I was just holding out for a second opinion. Luckily I live next to a Micro Center, they have conductive ink on the shelf! Are broken traces a common problem?

[fslice]

Thanks for the reply! Yeah, I figured I'd have to open it up and then bolt-mod it. I was just holding out for a second opinion. Luckily I live next to a Micro Center, they have conductive ink on the shelf! Are broken traces a common problem?

Its not uncommon. You can expect this to happen if a drink is spilled onto the membrane - I ruined a Unicomp by spilling soda on it which dissolved a number of traces. I fixed it as described, and it's what I'm typing on now.

Before you rip out the rivets, you can also check the controller PCB. It's possible that some solder joints are corroded affecting the 6 traces, considering your keys either 100% work or 0% work for any line. Check everything else before doing something irreversible.

[HanSoloCup]

Before you rip out the rivets, you can also check the controller PCB. It's possible that some solder joints are corroded affecting the 6 traces, considering your keys either 100% work or 0% work for any line. Check everything else before doing something irreversible.

Sorry, I'm a bit confused. Do you want me to check the slot where the ribbon cables of the membrane are inserted?

[Darkshado]

He's talking about that, but also the various solder joints on the controller's PCB.

You could also take a pencil eraser and gently remove some of that corrosion on the membrane contacts, shouldn't hurt. (The part on the membrane that goes into the connector on the PCB)

[HanSoloCup]

He's talking about that, but also the various solder joints on the controller's PCB.

You could also take a pencil eraser and gently remove some of that corrosion on the membrane contacts, shouldn't hurt.

Yeah, I did that, and gave it another go just in case. No change. The PCB's okay, I checked every trace with a multimeter.

[Darkshado]

Did you check the capacitors as well?

Although given fslice's analysis and your reported issues I'm leaning towards membrane problems as well.

IMO it's time to look into screw / bolt modding.

[Pumaeggs]

yeah 99% chance its the membrane traces fslice outlined. Also, its a little bit more work but i'd highly recommend a bolt mod over a screw mod for this guy. The screw mods are unreliable, feel kinda funky, and are very hard to undo and redo multiple times without ruining the barrel plate. Man that's gonna be a fun mod, it took me like 6 hours with my 102 key terminal board. Good luck my son

[watchman]

It seen like same problom I fixed it before.

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